Conversion String to Date

Question

How can I convert a string like YEAR,WEEK OF THE YEAR, DAY OF
THE WEEK to YEAR,MONTH,DAY???
I can do this :
SELECT SYSDATE, TO_CHAR(SYSDATE,'YYYYWWD') FROM DUAL;
SYSDATE TO_CHAR
07-DEC-01 2001496
But i need the inverse
Help
Thanks
Cleber

Answer 1

I'm not sure if this is the most elegant solution, but it seems
to work.
SQL> CREATE OR REPLACE FUNCTION get_date_week
  2   (v_string IN VARCHAR2)
  3  RETURN DATE AS
  4  
  5   v_first_day DATE := TO_DATE('01-JAN-' || SUBSTR
(v_string,1,4));
  6   v_date_week DATE;
  7   v_date_char VARCHAR2(20);
  8 
  9  BEGIN
10      FOR i IN 0..365
11      LOOP
12     
13   v_date_week :=  TO_DATE(v_first_day + i);
14   v_date_char :=  TO_CHAR(v_date_week, 'YYYYWWD');
15   
16   IF  v_date_char = v_string
17   THEN  RETURN v_date_week;
18   END IF;
19 
20     END LOOP;
21  END;
22  /
Function created.
SQL> SELECT get_date_week('2001496')
  2  FROM dual
  3  /
GET_DATE_
07-DEC-01
SQL> SELECT get_date_week('2001496')
  2  FROM dual
  3  /
GET_DATE_
07-DEC-01
SQL> SELECT get_date_week('2001497')
  2  FROM dual
  3  /
GET_DATE_
08-DEC-01